C# 正则表达式匹配两个或多个字符，并将每个字符替换为X

我想将两个或更多字符的任意组合

[fli]

更改为

x

。单独的

f

、

l

或

i

应保持不变，但任何组合都应更换

换句话说：匹配模式

[fli]{2，}

，并将其替换为

x

（与匹配长度相同）

示例输入1：

office/offices/muffled/stiffly/shuffled/different/difficult/office/officers no change: igloo/visiting/unwieldly

样本输入2：

oflice/oflices/muflled/stiflly/shuflled/diflerent/diflicult/ofiice/oflicers no change: igloo/visiting/unwieldly

样本输出（1和2相同）：

---

我使用的是C#，但我更愿意让它作为一个普通的正则表达式工作。

通过使用“向前看”和“向后看”找到了一个解决方案

string output = Regex.Replace(input, "([fli](?=[fli])|(?<=[fli])[fli])", "x");

string output=Regex.Replace（输入，”（[fli]（？=[fli]）|）（？如果您需要，您将发现。尤其是重载

上述屠宰和生产的产品符合预期

Now xxxp, xxop and xxy,
I don't care xx I die,
Now xxxp, xxop and xxy,
I don't care xx I die.
Don't ever leave me,
Don't ever say goodbye.

不知道为什么这会被否决？
string source      = @"
  Now flip, flop and fly,
  I don't care if I die,
  Now flip, flop and fly,
  I don't care if I die.
  Don't ever leave me,
  Don't ever say goodbye.
  " ;
Regex  rx          = new Regex( @"[fli]{2,}" ) ;
string replacement = rx.Replace(source, m => new string('x',m.Length)) ;

Now xxxp, xxop and xxy,
I don't care xx I die,
Now xxxp, xxop and xxy,
I don't care xx I die.
Don't ever leave me,
Don't ever say goodbye.